Walnut is a darker sounding wood and can sound choked a bit or dull.  That was my response to the die cast rims on the 14 x 5.  With the 2.3mm rims the drum still has a dark “bark” and more high-end cut.  These are great drums for blues and jazz.  I also like walnut on 12″ and 13″ drums.  Especially 12″ snares where the high notes combines with the low walnut tone to make a very cutting drum.  One of my favorites in all of my snares is my 1″ thick 12×5.5 walnut stave.  It is great for funk, punk, or any situation where cutting through a mix is important.  I used a very similar drum in the studio and on the road with Frankenfinger with excellent results.  I’m a big fan of 12″ snares.  The key is to buy a good one.  These cheap ones from the “major” manufacturers suck.  They are not able for use as a primary snare.  They are “effect” drums.  Ply drums and metal drums make poor 12″ snares (except Brady ply drums!).  A 12″ snare should be a stave and hopefully a walnut, jarrah, or even a mahogany one. They should also be 5″ deep or deeper.  If you are looking for a 12″ snare, trust me, don’t buy one of these cheapo snares.  It will sit in its case or be sold on Ebay at a loss.